The method and apparatus here disclosed is addressed in general to stage cementing, and is related particularly to means for dispensing or injecting fluidized cement under pressure, into vertically spaced apart levels of a substrate which surrounds the casing of a hydrocarbon producing well. The apparatus includes a cement dispensing head, also identified as a staging collar, having a casing which is adapted at one end to communicate by a pipe string, to a source of the fluidized cement. The injected cement will form a continuous sheath about the casing exterior.
The dispensing head or staging collar includes a casing having a central chamber or passage with an opening at the lower end for discharging fluidized cement during a first cementing stage, into a first level of the substrate. One or more secondary, or lateral openings formed in the casing wall subsequently conduct cement during a second stage, into a second level of the substrate.
In a stage collar of the type contemplated, a plug or closure member carried into the casing on the downward flow of fluidized cement, engages an annular seat at the casing lower end thereby interrupting the downward cement flow and terminating first stage flow. Resulting back pressure actuates a flow control member to open the secondary discharge ports and divert the cement flow therethrough.
After the initial cementing stage, a multi-segment sleeve operably registered in the casing central chamber is displaced from a retracted position to a forward position Functionally, in the forward position the sleeve segment closes the lateral cement discharge ports and discontinues cement flow therethrough at the end of the second stage.
A first segment of the flow control sleeve in the stage collar includes an annular shoulder which will sealably engage a flow carried opening plug, thereby to preclude further cement flow therethrough during the first stage. A second segment of the flow control sleeve includes a second annular seal which engages a second wiper plug to discontinue cement flow.
In the event the cement flow regulating sleeve becomes inoperable to control cement flow as a result of improper action of the wiper plug, or for other reasons, means is known to forcefully adjust or displace the sleeve section into closing position. In any instance, it is necessary to actuate the flow control sleeve in a manner to assure that the casing lateral discharge openings are closed to cement flow.